Bridge truss



Dec. 21 1926.

C. A. P. TURNER BRIDGE TRUSS Filed August 21. 1924 T Snoznboz: R TURNER;

Patented Dec. 21, 19.26.

I hli ili'ii fiw i i rh i hlg r tT'l CLAUDE LA. 1?. TURNER. 0F MINNEAPOLIS, MIIQ'NESOTA, AfiSIGNQR TO WILLIAM lliI. TURNER, OE IVHIENEAPOLIS, MINBIESOTA.

BRIDGE TRUSS.

Application filed August 21, 1924.

My invention relates to bridge trusses, and, more particularly, to the form of triangulation and to the make up of posts, chords and floor system by which I can increase the stillness greatly and save twenty-five percent of the weight under general practice. It has heretofore been the custom to limit the length of the main truss floor panels to a maximum of one and one-half times the width, center to center, of trusses as required by the American Railway Engineering Association specifications. This requirement is made so that the angularity of the laterals be not too flat, this being fixed in the pin con nected truss by the length of the floor panel. I propose to make the trusses of riveted construction and use floor panels much longer than have been used before discarding the subdivision of the main truss frame in long spans. I succeed in doing this by making the length of the lateral panels of the floor system an even fraction of the. length of the truss panels. The lateral system of the floor thus becomes a double intersection lVa-rren system which enables the top flanges of the stringers to be more ri idly braced by Y- frames from the attachments of the laterals at the bottom flange to points vertically above in the compression flange of the stringer instead of by Warren bracing of the top stringer flange following the common practice.

lVith the long truss panels, omitting the sub-struts of the Baltimore or sub-divided Warren system, the web members in the long span become relatively very long and require rigid lacing in the plane of bending, due to the dead weight of the member. For long spans 1 have devised an eight-angle section shown in Fig. 6 in which eight angles are laced by channel sections with the Webs of the channels parallel to the plane of the truss on the sides of the web member and normal to the back and underside of the member on the adjacent faces, thus securing a section that is not only rigid under simple bending but very rigid under torsional stresses and which can be very readily spliced where the lengths exceed the lengths of the angle sections ordinarily rolled. Failure of angle iron sections generally takes place by the crippling or buckling of the outstanding flange of the angles. It will be noted in the sections I propose using, that all flanges are turned inward facilitating connections Serial No. 733.355.

of the sway bracing and obviating an unsupported projecting flange. The flatwise channel lacing on. the sides with web parallel to the plane of the truss coacting with the reverse position of the channel on the back and under side, gives a rigid support against this tendency at the connections and between the latticing. When thesize of the member warrants, I propose to insert castings which tie the flanges together, thus making a novel and exceptionally rigid member. In the make-up of the top chords (cross section Fig. 8) to reduce shop work I propose the use of two beams and a cover plate for the section introducing the novelty of elimination of latticing on the lower flange and obviating its pantograph action under compression by the adoption of a series of closely spaced diaphragms from four to seven feet apart dependent on the size of the beams used in the make-up oi the chord. The make-up of the chord and end post thus becomes cellular in character. The stiffness of the cover plate supported crosswise and lengthwise in rectangular compartment-s, under normal forces would be twice or three times as rigid as when the diaphragi'ns were not employed and the same statement is true regarding the similar sections of the webs of the beams and as the r sistance to crippling or buckling under coinpression is approximately proportional to the fiexural rigidity of the plate a large increase in resistance is attained by this cellular construction which is wanting where diaphragms are used'at long intervals apart following customary practice in the past. Where built up diaphragms have been commonly used in compression members, they have been spaced at relatively long intervals to supplement the staying effect of the lacing, while in my type of member the object is to eliminate lacing entirely. on the underside of the compression members and depend solely on the series of diaphragms for staying the bottom flanges of the section and resisting lat-- eral displacement and torsional effects. The floor stringers, because of the length of the panel, are necessarily plate girders which in order that the depth may not be excessive are made continuous by splicing them above or thru the supporting floor beams instead of framing them into the floor beam discontinuously as h as been the customary practice. The customary practice in the railroad bridge is to make the floor beam deeper than the stringer, but in my type of truss because the stringer is relatively two or three times as long as it is ordinarily made, the economic depth of the stringer is greater than for the floor beam and its flanges are spliced across or over the latter producing a different distribution of moments, a large increase in stiffness and reduction of flange section.

The full objects and advantages of my invention will appear in connection with the detailed description thereof, and the novel features in my inventive idea will be particularly pointed out in the claims.

In the accompanying drawings, which illustrate an embodiment of my invention,--

Fig. l is a side elevational view of the truss. Fig. 2 is a floor plan view. Figs. 3, 4 and 5 are detail views showing the stringer and beam connections. Fig. 6 is a sectional View of a post. Fig. 7 is an elevational view of the post. Fig. 8 is a view in section of the top chord. Fig. 9 is a view in section on the line 00-00 of Fig. 8. Fig. 10 is a view in section showing the cross frame.

Referring to the construction shown in the drawings, the bottom chord panels are indicated a, 1, 2 and 8 from one end toward the center and a, 1', 2 and 8 from the other end toward the center. Panel points are indicated at b, c and (Z from one end towards the center panel point e and at Z), c and d from the other end toward the center. As shown in Fig. 2, it will be noticed that the laterals Z Z, Z and Z divide the bottom panels into three lengths so that their inclinations to the chords is that of a favorable angle, whereas if the laterals were run from Z to Z, following the common custom the truss would be lacking in rigidity. Bottom lateral bracing is indicated at L and top lateral struts at T. Referring to Figs. 3 4i and 5 the stringers are indicated at S and the beams are indicated at B. In this detail I have made the stringers deeper than the beams and spliced them across the top of the beams, and reinforced them with a plate below the beams, thereby securing continuous action and great rigidity of the floor in a new and novel manner. The posts P, P, etc., are made up of ei ht angles laced with channels on the sides parallel to the plane of the truss, as shown in Fig. 7, and laced transversely by channels which impart great torsional rigidity to the section. The top chord is preferably made of deep I-beams E having a cover plate 0 with cast steel diaphragms D, thereby eliminating the need of lacing which is commonly used in bridge members to stiffen up the section.

I claim:

1. In a riveted truss frame for a railroad bridge structure, the combination of beams and long floor panels having lateral panels an even fraction thereof with plate girder stringers continuously spliced at the beams throughout the floor.

2. In a riveted truss frame for a railroad bridge structure, the combination of beams, lateral braces, main later-a1 members and long floor panels having lateral panels an even fraction thereof with stringers continuously spliced at the beams for the length of the floor, flanged strin ers rigidly riveted to the lateral braces with the top flanges-of said stringers braced by cross frames extending upwardly from the connection of the main lateral members to the bottom flanges of the stringers.

8. In a camel back riveted truss, cellular type of chords made of Lbeain sections and cover plates braced by a series of closely spaced diaphragms intermediate the length of the chords riveted to the Webs of the beams, to the cover plates and to the inner flanges of the beams.

i. In a camel back riveted truss, the combination of posts made up of eight angles arranged in pairs at each corner with channel bar lacing riveted to both angle legs turned in the same direction transversely and channel bar lacing parallel to the plane of the truss.

In testimony whereof I hereunto aiiix my signature.

CLAUDE A. P. TURNER. 

